Explosives and method of blasting



United States The invention relates to an improvement in explosives and more particularly relates to improved light metalcontaining explosive compositions wherein the light metal component and explosive component are volumetrically coextensive, and to a method of blasting therewith.

This application is a continuation-in-part of my copending application Serial No. 836,879 now abandoned filed August 31, 1959.

In preparing and using a slurry similar to the light metal-containing ammoniated ammonium nitrate compositions described in a copending application Serial No. 784,895 filed January 5, 1959, now Patent No. 3,094,443 issued June 18, 1963, a problem arises that if the slurry is formulated from substantially equiaxed particulated light metal in the particle size range passing from about a No. 20 sieve (U.S. Sieve Series) to about a No. 200 sieve, the so-formulated slurry does not remain homogeneous on standing. The metal particles tend to settle rapidly.

It is accordingly the principal object of the present invention to provide a light metal-containing ammonium nitrate explosive composition which retains substantially uniform distribution of said light metal throughout the explosive composition on standing.

It is a further object of the present invention to provide an improved metal-containing ammonium nitrate explosive composition which is readily mixed at the blast site.

Another object of the present invention is to provide an improved light metal-containing ammonium nitrate explosive composition which is readily prepared from inexpensive particulated forms of light metal.

Another object of the present invention is to provide an improved light metal-containing ammonium. nitrate explosive composition which exhibits enhanced work potential on detonation yet is not unduly shock sensitive.

Still a further object of the invention is to provide an improved method of blasting with a light metal-containing ammonium nitrate explosive composition.

These and other objects and advantages of the invention will be better understood on becoming familiar with the following specification and claims.

The invention is predicated on the discovery that upon admixing a particulated light metal of low bulk density with a bulk explosive, for example a liquid solution containing at least 60 weight percent of ammonium nitrate dissolved in liquid ammonia, water, or mixtures thereof, the metal and the solution phases being substantially volumetrically coextensive, and the metal being selected from the group consisting of magnesium, magnesium-base alloys, aluminum, aluminum-base alloys, magnesium-aluminum alloys and mixtures thereof, an explosive composition is obtained having a good work potential on detonation but only moderate sensitivity to detonation as by shock. Upon suitably loading a bore hole with the explosive composition of the invention, and providing the requisite initiation therefor, improved blasting results are obtained.

The particulated light metal used in the composition of the invention is conveniently selected from machine chips, flakes or band saw filings obtained as scrap from conventional cutting, cleaning and machining operations, or shredded or sheared foil may be used if desired. In any event, the particulated metal should have an effective bulk atet density (pour or light tap) in the range of from about 0.0% to about 1.0 gram per cubic centimeter in the composition, the most preferred bulk density varying directly with the percent metal employed. The metal particles preferably are nonequiaxed as in the case of foil pieces, or curved or elongated as in the case of shavings whereby close packing of the particles does not readily occur. In utilizing the said embodiment of the instant invention, normally in the confinement of a bore hole, or a suitable container, as in testing, for example, a quantity of Divers liquid is admixed with a suitable proportion of the particulated light metal toform a volumetrically coextensive mixture.

Divers liquid is a substantially saturated solution of ammonium nitrate in anhydrous liquid ammonia. A saturated solution of ammonium nitrate in ammonia under conditions of atmospheric pressure and ambient temperature will generally contain from about 15 to about 30 percent by weight of ammonia but more generally from about 20 to about 25 percent by weight of ammonia.

In selecting the form of particulated metal for use in preparing the composition, it is advantageous from the standpoint of efiicient power production on detonation to use metal particles which in bulk have just about the requisite void space to contain a predetermined amount of ammonium nitrate solution and thus to obtain a relatively uniform distribution of metal and liquid phases on commingling the two. However, a small head of liquid solution above the solid metal does not adversely affect detonation velocity or power. While the exposure of a small amount of metal is likewise not particularly harmful, it is generally desirable to at least cover the metal phase to obtain the maximum benefits from the metal. It will then be appreciated that in order to maintain volumetrically coextensive the liquid and metal phases, a particula-ted metal having a low bulk density is to be employed in mixtures of low metal content and, on the other hand, particulated metal of relatively high bulk density is to be employed in mixtures of high metal content.

To illustrate the improved method of blasting according to the instant invention, a composition of a light metal and ammoniacal ammonium nitrate solution wherein the metal and the solution are volumetrically coextensive is prepared and charged at the blast site in one of several ways. If the bore hole is readily accessible or if a confining container is used, since in any case confinement of the explosive charge is conducive to obtaining a complete and powerful detonation, it may be preferred to transfer a predetermined amount of the ammonium nitrate solu tion to the bore hole or container and then to add the requisite amount of particulated light metal to make the solid and solution phases practically coextensive. If an anhydrous ammoniacal solution is used, it may be preferred to put the metal in place first before the cold anhydrous ammoniacal solution collects atmospheric moisture, and to add the said solution to the metal until the metal is just covered. In loading inaccessible bore holes, it may then be preferred to admix the metal and nitrate solution in a suitable container, such as a bucket or plastic bag or other open container, adjust the relative amounts of solid and liquid phases, and pour or otherwise transfer the composition into the bore hole. A primary detonator, such as a No. 8 electric blasting cap alone, or a length of 50 grains per foot high velocity fuse cord, such as Primacord armed with an electric blasting cap, or other more powerful detonators such as a pentolite booster, shaped charge or tetyl booster is then lowered or inserted into the mix preferably near the bottom thereof. Lead wires or a fuse are then run from the initiator to a suitable firing mechanism. Tamp or stemming material, such as sand or gravel, as conventionally used provides adequate confinement of the load in the bore hole. Upon activating the firing mechanism and firing the detonator, the ammonium nitrate explosive composition detonatcs with an excellent blasting power comparable or even greater than that obtained for ammonium nitrate mixtures containing apprecilength of 50 grain per foot Primacord was inserted into the mixture, armed with a No. 8 electric blasting cap, and the bottle stoppered. Upon initiating the blasting cap, the explosive mixture was detonated. There was a able amounts of a conventional explosive, such as gelatin 5 l d report d the barographic recorder indicated a dynamltemaximum impulse of 14.8 millimeters.

examplesbof P P i Frames of i As a further example of the instant invention, about f; qjg g i g g o igf g fgg ig g l z f g 50 pounds of a 50-50 weight percent mixture of coarse g s S ga me 1 en me e 5 an 1 magnesium and aluminum chips and 45. pounds oi an detonated. In each case, the particulated metal was placed 10 a ueous ammoniac a1 solufio of nitmt in the bottle and caused to occupy a volume of about a f f t 4 6 6 con total of 100 cubic centimeters in this bottle. Divers liquid E mg a P Wa f was poured over the metal thereby forming substantially bfllance m n F were Placed a Plague volumetrically coextensive phases of the metal and the e t wheremfhe'y ocPupled a Volume of abpllt liquid. The remainder of the bottle was then filled with 15 cublc P In fills 9 metal and flllld Wfife sand stemming. Some of the mixtures were detonated by substantlally volumeillcally COBXteIlSll/e and the efiectlve two inch lengths of 50 grains per foot Primacord (a high bulk density of the metal in the composition Was about velocityfuse cord containing pentaerythritol tetranitrate) 0.8 gram per cubic centimeter. Thecontainer was ininserted into the mixture and armed with a No. 8 electric t d i t a bor hole about six feet deep, armed with blastlllg P- other mlXtureS were detonated y a 3 20 a shaped charge initiator, the hole stemmed and the load electric blasting cap alone. Bottles were stoppered after then d6t0flate A blast of very good efiidency resulted. i i il of eachf deaonatlon l i Among the advantages of the invention are the simple 33551123303365?) tiefiiiiiimimiiifii 211222113; lhhhihg hhhhhhhh hhhhhhd hhh the hatch Whh which i nen om sit tr n of the detonation. The mixtures tested and the test results isigig gf g ite ts of the c I p0 Ion may be a s are listed in the following table. Po 6 a b ad th Also listed in the table are the results of experiments f mo 1 ca i can 6 m K e Pmsant carried out as comparison or blank tests. In these experivenuon Wlthout dePal'hmg z P Scope f ments, variously, detonations of initiators in the presence for It 15 understoPd that I m y y as defined 1n and'absence of Divers liquid were recorded. i116 pp clalms- Composition, Effective r percent by wt. bulk graphic Metal 01' Source density impulse, Test No. alloy and form of metal Detonator mm. Visual and audio observations Divers Partiof metal in pressure liquid culated container, rise metal grams/cc.

1 97 3 cell Mg... MC..-.- 0.018 Primacord 3.4 ioudcr report than 2 95 5 -.-do MG.. 0.03 10.8 Grand report, smoke, trace of T6. 3 90 .06 10.5 Very good report, flash, smoke. 4-- s5 0.09 9.5 Do. 5. 80 0.12 11.6 Sharp fast report, flash, smoke. 6-- so 20 0.12 11.5 Do. 7-- 20 0.12 15.3 Do. 8- 80 20 0.12 16 .8 Good report, large flash. 9-- 10 0.06 7.2 Do. 10. 97 3 0 .018 13 .3 Good report, no flash. 11-- I 5 0.03 14.1 Excellent report, no flash. 12-- 90 10 0.06 16.6 Very heavy detonation, flush. I 13.. 85 15 0.09 16.7 Do. 14-- 80 20 0.12 17.2 Very heavy detonation, fire. 15-- 90 10 0.06 14.1 Very heavy detonation, flash. 16.. 80 20 0.12 20.6 Very heavy detonation, fire. 17.- v 85 15 0.09 6.6 Good report, flash. 18-- 80 20 0.12 6.4 Very good report, flash. 19.- 90 10 0 .06 6.1 Good report, no flash. 20 80 20 0.12 9.8 Very good report, flash. Blank 1.... 3.7 Weak report, little smoke.

(ave. of 3) Blank 2.... 100 1.3 Very weak report. Blank 3.--. 2.4 Do. Blank 4..-. 2.0 Do.

1 Total Explosive load-60 grams.

Cell Mg=magnesium of purity grade as obtained from electrolytic cells. ZK61=magnesium-base alloy having as nominal composition 6 percent Zn, 1 percent Zr, balance Mg. AZ31=magnesium-base alloy having as nominal composition 3 percent Al, 1 percent Zn, 0.2 percent Mn, balance Mg. MO=machine chips, generally of spiral shape, bulk density (light tap) about 0.035. to 0.1, surface area about 39 sq. in per. gram.

RF=rotary filings, bulk density about 0.2 gram per cubic centimeter.

BD=baudsaw dust, bulk density about 0.2 gram per cubic centimeter. F0 =foil chips prepared by cutting 0.0008 inch thick household foil wrap into pieces about 0.25 inch by 1 inch, surface area about 66 sq. in. per gram.

GG= Griguard chips, pharmaceutical grade, chip size about 0.010 by 0.125 by 0.5 inch, bulk density about 0.23 gram per cubic centimeter.

No. 8 E.B.O.=No. 8 electric blasting cap. By way of an additional example of the practice of the invention, 6 grams of aluminum foil chip-s prepared by cutting commercial aluminum foil Wrap having a thickness of about 0.0008 inch into pieces about 0.25 inch by 1 inch were placed in a similar cubic centimeter glass bottle. These occupied a volume of about 100 cubic centimeters and were covered by 54 grams of a saturated water solution of ammonium nitrate. The effective bulk density of the metal in the composition Was about 0.06 gram per cubic centimeter. A 2 inch for said ammonium nitrate, said solvent being selected" 3,1aao29 from a group consisting of liquid ammonia, water and mixtures thereof, said light metal chips and said liquid ammonium nitrate based component being substantially volumetrically coextensive and said metal having an effective bulk density in said composition of between about 0.03 and about 1.0 gram per cubic centimeter.

2. The improved metallized ammonium nitrate exp1o sive composition comprising a solution of ammonium nitrate in a solvent selected from the group consisting of liquid ammonia, water and mixtures thereof, said solution containing at least 60 weight percent of ammonium nitrate, and particulated non-equiaxed light metal chips selected from the group consisting of magnesium, magnesium-base alloys, aluminum, aluminum-base alloys and mixtures thereof, whereby close packing of said particulated light metal does not readily occur, said particles of said light metal having an effective bulk density in said composition of from about 0.1 to about 0.8 gram per cubic centimeter and said solution and said particulated light metal being substantially volumetrically coextensive.

3. The improved method of blasting which comprises commingling in a bore hole about equal volumes of a mixture of a coarse non-equiaxed aluminum and magnesium chips and a solution of ammonium nitrate, said mixture of chips being composed of about 50 weight percent of 6 aluminum and magnesium and said solution containing from about 4 to about 6 percent water, 25 to about percent ammonia, balance ammonium nitrate, said mixture of chips having an effective bulk density in the composition ranging from about 0.10 to about 0.80 gram per cubic centimeter and said mixture of chips and said solution being substantially volumetrically coextensive, arming the commingled solution and chip mixture with a detonator therefor, stemming said commingled solution and particulated light metal and initiating said detonator.

References Cited in the file of this patent UNITED STATES PATENTS 2,393,594 Davis Jan. 29, 1946 2,451,864 OBrien Oct. 19, 1948 2,703,528 Lee et a1. Mar. 8, 1955 2,704,515 Barlow Mar. 22, 1955 2,816,012 Walton Dec. 10, 1957 2,836,484 Streng et a1 May 27, 1958 2,903,969 Kolbe Sept. 16, 1959 2,951,752 Stevenson ept. 6, 1960 2,968,542 Brock Jan. 17, 1961 2,992,086 Porter July 11, 1961 3,044,911 Fritzlen July 17, 1962 3,056,701 Fritzlen Oct. 2, 1962 

1. A METALLIZED AMMONIUM NITRATE EXPLOSIVE COMPOSITION COMPRISING PARTICULATED, NON-EQUIAXED, LIGHT METAL CHIPS SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, MAGNESIUM-BASE ALLOYS, ALUMINUM, ALUMINUM-BASE ALLOYS AND MIXTURES THEREOF AND A LIQUID AMMONIUM NITRATE BASED COMPONENT, SAID AMMONIUM NITRATE COMPONENT COMPRISING A MIXTURE CONTAINING AT LEAST 60 WEIGHT PERCENT AMMONIUM NITRATE IN COMBINATION WITH A SOLVENT FOR SAID AMMONIUM NITRATE, SAID SOLVENT BEING SELECTED FROM A GROUP CONSISTING OF LIQUID AMMONIA, WATER AND MIXTURES THEREOF, SAID LIGHT METAL CHIPS AND SAID LIQUID AMMONIUM NITRATE BASED COMPONENT BEING SUBSTANTIALLY VOLUMETRICALLY COEXTENSIVE AND SAID METAL HAVING AN EFFECTIVE BULK DENSITY IN SAID COMPOSITION OF BETWEEN ABOUT 0.03 AND ABOUT 1.0 GRAM PER CUBIC CENTIMETER.
 3. THE IMPROVED METHOD OF BLASTING WHICH COMPRISES COMMINGLING IN A BORE HOLE ABOUT EQUAL VOLUMES OF A MIXTURE OF A COARSE NON-EQUIAXED ALUMINUM AND MAGNESIUM CHIPS AND A SOLUTION OF AMMONIUM NITRATE, SAID MIXTURE OF CHIPS BEING COMPOSED OF ABOUT 50 WEIGHT PERCENT OF ALUMINUM AND MAGNESIUM AND SAID SOLUTION CONTAINING FROM ABOUT 4 TO ABOUT 6 PERCENT WATER, 25 TO ABOUT 35 PERCENT AMMONIA, BALANCE AMMONIUM NITRATE, SAID MIXTURE OF CHIPS HAVING AN EFFECTIVE BULK DENSITY IN THE COMPOSITION RANGING FROM ABOUT 0.10 TO ABOUT 0.80 GRAM PER CUBIC CENTIMETER AND SAID MIXTURE OF CHIPS AND SAID SOLUTION BEING SUBSTANTIALLY VOLUMETRICALLY COEXTENSIVE, ARMING THE COMMINGLED SOLUTION AND CHIP MIXTURE WITH A DETONATOR THEREFOR, STEMMING SAID COMMINGLED SOLUTION AND PARTICULATED LIGHT METAL AND INITIATING SAID DETONATOR. 